Meteorology Quiz: Breezes and Winds

Wildland Fire Behavior Terminology

• Point of origin: Exact place of initial ignition where combustion begins.
• Head of a fire: Fastest spreading side of a fire.
• Flank of a fire: Area adjacent to the main direction of fire spread.
• Rear of a fire (heel): Slowest portion, spreading against the wind or downhill.
• Fire perimeter: Total outer edge of a fire.
• Fingers of a fire: Narrow extensions extending from the main fire body.
• Pockets of a fire: Unburned areas within fire edge, surrounded by fingers or slower burning sections.
• Island: Unburned fuel zone inside fire perimeter.
• Spot fire: New fire ignited outside the main fire perimeter by embers.
• Smoldering: Fire behavior characterized by no flame and minimal spread.
• Creeping fire: Slow-spreading fire with low flames.
• Running fire: Rapidly spreading fire with a clear head.
• Spotting: When fire sends sparks or embers beyond its main ignition zone.
• Torching: Ignition of leaves/foliage of trees from the bottom, typically small groups.
• Crown fire: Fire reaching the tops of trees, may be independent of surface fire.

Fire Behavior and Control

• Flare up: Sudden increase in fire spread or intensity, often short-lived.
• Firewhirl: Vertical vortex of heated air, smoke, and gases from a fire, unpredictable in movement.
• Anchor point: A barrier to fire spread used as a starting position for fireline construction.
• Control line: All constructed or natural barriers plus treated fire edges for containment.
• Fireline: Area of the control line that has been cleared down to mineral soil.
• Mop-up: Procedure of extinguishing near control lines to prevent flare-ups.
• Contained: Fire status indicating that control lines are complete, expecting to prevent spread.
• Controlled: Completion of control lines around the fire, including buffers to manage hot spots.

Fire Triangle and Heat Transfer

• Three elements of the fire triangle: Fuel, air (oxygen), and heat.
• Three methods of heat transfer: Radiation, convection, and conduction.
• Radiation: Heat that can dry or ignite surrounding fuels.
• Convection: Upward movement of warm air and embers creating a smoke column.
• Conduction: Heat transfer through direct contact between fuel particles.

Topography's Role in Fire

• Topography: Arrangement of the earth's features, affecting fire spread.
• Aspect: Slope direction regarding sun exposure; influences fuel moisture and fire behavior.
• Box canyons: Fires in these areas can have accelerated reactions similar to flames in enclosed spaces.
• Narrow canyons: Eddies and strong winds can spread fire across to opposing sides.
• Ridges: Fire may change direction when ridges meet canyons due to airflow.
• Saddle: Wind through mountain passes increases speed and may cause erratic fire behavior.

Fuel Dynamics

• Fuel characteristics affecting fire behavior: Type, loading, and availability.
• Fuel types: Grass, grass-shrub, shrub, timber-understory, timber litter, and slash-blowdown.
• Fuel loading: Weight of fuel per unit area, indicating potential intensity and spread.
• Surface Area to Volume Ratio: Smaller fuels burn quicker due to higher surface area exposed to air.
• Fuel arrangement: The spatial distribution of fuels; can be horizontal or vertical, affecting fire spread.
• Vertical arrangement: Includes ground, surface, ladder, and aerial fuels, contributing to fire intensity.
• Fuel moisture: Determines ignitibility and burning efficiency, affected by weather conditions.

Weather and Fire Behavior

• Fire weather principles: Temperature, relative humidity, precipitation, atmospheric stability, and wind patterns.
• Relative humidity (RH): Levels inversely related to temperature; affects fuel moisture.
• Atmospheric stability: Influences upward air movement; unstable conditions promote fire intensity.
• Indicators of stable and unstable atmospheres: Variations in cloud formation, visibility, and wind patterns often signal fire behavior changes.
• Critical fire weather conditions: Strong winds, low humidity, high temperature, and dry thunderstorms can trigger severe fire risks.

Wind Effects on Wildland Fires

• General winds: Larger scale, resulting from atmospheric pressure systems, usually flowing west to east.
• Local winds: Terrain-influenced winds including upslope and downslope variations.
• Specific wind characteristics: Variability in speed and direction throughout the day significantly impacts fire dynamics.### Weather and Fire Risks
• Warm conditions for the season can lead to increased fire risk.
• Winds can persist for several days, often reaching speeds of 40-60 mph.
• Relative humidity (RH) decreases as winds pick up.
• High wind speeds combined with low RH create ideal conditions for rapid fire spread.

Common Foehn Winds in the Western US

• Chinook Wind: Found along the eastern Rockies and east of Sierra Nevada.
• Wasatch Wind: Occurs on the western side of the Wasatch Range in Utah.
• Santa Ana and Sundowner Winds: Affect Southern California.
• Mono and North Wind: Influence central and northern California.
• East Wind: Present in western Washington and western Oregon.

Thunderstorm Risks for Firefighters

• Winds associated with thunderstorms can shift, altering fire behavior and intensity.
• Rising heat from fires can create strong convection columns, potentially forming thunderstorms.
• Thunderstorms can produce hazardous downdrafts, increasing fire danger.
• Lightning strikes pose additional risks for igniting new fires.

Dust Devils

• Serve as indicators of unstable air conditions in hot, dry weather.
• They typically form over dry ground on clear days with light winds.

Firewhirls

• Generated by intense heat from wildfires.
• Capable of lifting large, burning embers and spreading them beyond the main fireline, causing new spot fires.
• Often develop on the leeward side of ridges, where winds are sheltered.

Predictive Services

• Comprise a team of Interagency Land Management Fire Intelligence Coordinators and Fire Meteorologists.
• Conduct seasonal assessments to evaluate fire risks.
• Provide forecasts for 7-day significant fire potential and monthly outlooks.
• Offer briefings and daily summaries to inform firefighting efforts.